Anyone setup a device for using excess solar for HWS


hi Wilburight, as far a i know the energy management is a straight on off switch, so yours is ON at 3500 watts inverter output, NOT 3500 watts been exported to the GRID, and the 500 watts of is again inverter output and not power drawn from the grid,
you can check this if you like by login direct to the inverter and then bringing up the screen that shows AC volts at the inverter== this will show when the hot water service is on by the volts drop in output at the inverter, as i am last on a very long grid line my 3.6 kw element causes a 5 volt drop in output voltage ,pair the pvorg screen and the inverter screen up and you will see the pv screen show output of 3500 watts and inverter screen sow volts drop when the heating element is on, in this way i worked out my house base load is 600 watts-- so my P Manger is turning on at 2500 watts means 2500-600 watts —1900 watts going to the hot water heating element so i am powering %53% of the hot water system with solar power, so if i use a 1200 watt element instead, then i have 100% solar power for my hot water, also in summer when the grid voltage is over 258 volts and the inverter de rates 600 watts because the of high volts i can set the power manger to turn on at 4800 watts, my inverter max output is 5040 watts, drop the grid volts down by heating water and get the output back to 5040 watts, so using 600 watts of solar power that would have not been generated because of high output voltage hope this helps Jim


I don’t think mine is configured like that -

I’ve set it to Power Surplus, so if the PV goes over the pre-set ‘Feed-In’ limit, but the 5kW A/C is on and pumping, then the HWS doesn’t get any power during the day (unless the PV’s making over 9kW or I manually switch its boost on).

When the A/C cycles to idle, Solarweb shows the appropriate consumption change as the HWS switches on - assuming its thermostat allows it. The ‘State’ shows ON when this excess power at Output: IO-1 is available, however the HWS may not be using it if it’s hot enough already and so that power goes to the grid instead.

PVOutput also shows these cycles, as below on a day when we were overseas. The shortest day of the year, however around midday the HWS decided it needed a top-up and the sun provided :slight_smile:


thank you for your helpful reply I can see from your data that you have a smart meter installed,
so your system is using exported energy not total output watts.

My system has NO smart meter,just the data manager and the relay so mine can only be set BY power production,:sunny::sun_with_face:


Wilburight, you have your power production threshold off set to consumption, but shouldn’t it be set to Feed In as well, like the on threshold? Presumably your HWS draws more than 500 W so the way you have set it the Fronius will never switch the HWS off. The HWS will always run until it switches itself off at the temperature pre-set.


Yes, I specified this along with the PV assisted HWS with the original PV system (3 phase) install 2 years ago. I think I was one of the first opportunities my (excellent) installer had at setting up the controlled HWS relay, so he was very happy with the result. As was I, since our rather large power bills dropped by 80 - 85%.

The ‘Controlling’ option is set to Power Surplus with ‘Feed-in Limits’. When feed-in to the grid exceeds the user-set threshold (e.g. 3500W), then the HWS relay trips making power available to the HWS element. Should this result in consumption (from the grid) exceeding 500W (e.g. 4000W total), then it trips it off. There’s an apparent delay before any subsequent attempt, so there’s no continual cycling off and on.

When the PVs are pumping out the necessary Watts, the Solarweb animation and PVOutput charts confirm the intended result.


Wilburight, since our rather large power bills dropped by 80-85 %
we have just had our first power bill for 12 months $62.80 total,and thats for winter here so we are very pleased with the way the relay works.


ok so after reading a few comments from places i may not be able to have a relay connected the the controlled load.
if i have to put it onto the peak side its not worth it.

I have also found a few plans that have a decent fit but the rates are higher. after discounts the fit and controlled load rate are about the same making it almost pointless to try and use my power generated.
if i put the hws on peak then i would surely lose out.

i was getting excited for this project but its unviable currently.


B-man do you use air con during the day if so you could use the relay to run that instead of hot water,
also that 62.80 $ is the total power used over 62 days in winter.


B-man or you could have fitted a 2 nd element in your hot water tank, so 1 fed from solar to heat the tank during the day and the 2 nd element from your controlled load,this is quite common i am told. so max use of solar and very little use of controlled load power.


i don’t even have an aircon yet but not a bad idea will have provisions for a relay but not install yet

i had a look at that but don’t have anywhere to install a second element


B-man most big tanks have a spare fitting for a second element,i can be a screw in type with its own temperature switch attached- it just need to be set a a lower temperature the the main element so it will work from solar to heat your water most of the time,usually they can be fitted in a spare pipe fitting blank hole near the bottom of the tank if you use a smaller element size,whick works best with solar anyway


just had a look. i have no spare holes in the tank